Brewer's: The Acmonian Wood
The trystplace of unlawful love. It was here that Mars had his assignation with Harmonïa, who became the mother of the Amazons.
“C'est là que ... Mars eut les faveurs de la nymphe Harmonie, commerce dont naquirent les Amazones”
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894